Computer historians recognise his contribution to their field by his construction at the age of 18 of a mechanical calculator capable of addition and subtraction (one of his original mechanical calculators is displayed at the Zwingermuseum, in Dresden, Germany). He also produced a treatise on conic sections as a young man. In 1654, prompted by a friend interested in gambling problems, he corresponded with Fermat and laid out a simple account of probabilities.

He later formulated Pascal's wager, an argument for the belief in God based on probabilities. His name is also attached to Pascal's triangle, a way to present binomial coefficients, which were, however, known long before his time.

His notable contributions to the fields of the study of fluids (hydrodynamics and hydrostatics[?]) centered around the principles of hydraulic fluids. His inventions include the hydraulic press (using hydraulic pressure to multiply force) and the syringe. He clarified concepts such as pressure (the unit of which bears his name) and vacuum.

Following a profound religious experience in 1654, Pascal abandoned mathematics and physics for philosophy and theology. In 1660, Pascal's The Provincial Letters[?], a defense of the JansenistAntoine Arnauld, was ordered shredded and burned by King Louis XIV of France. His most influential work, the Pensées, was never completed, but a version of his notes for that book were published in 1670, 8 years after his death, and it soon became a classic of devotional literature.

Pascal is also known for his attack on Casuistry as a popular ethical method used by Catholic thinkers in the early modern period, (especially the Jesuits) as the mere use of complex reasoning to justify moral laxity. His writings on this subject were published as the Lettres provinciales[?], or "Provincial Letters."